Emma's friend Megan lights up a cigarette every chance she gets — while she's cruising around with their friends on Friday nights, during breaks at the pizza place, before soccer scrimmages, even as she babysits her brother. Emma's worried — both for her friend's health and for her own. She's not sure Megan realizes how her habit could be affecting the health of the people she smokes around.

Everyone knows smoking is a bad idea. And by now you've probably heard that breathing in someone else's secondhand smoke is also hazardous to your health.

What Is Secondhand Smoke?

Secondhand smoke comes from both the smoke that smokers exhale (called mainstream smoke) and the smoke floating from the end of the cigarette, cigar, or pipe (called sidestream smoke).

It may seem pretty harmless, but secondhand smoke actually contains thousands of chemicals — from arsenic and ammonia to hydrogen cyanide — many of which have been proven to be toxic or to cause cancer (called carcinogens). High concentrations of many of these chemicals are found in secondhand smoke. In fact, secondhand smoke significantly increases a person's risk for:

• respiratory infections (like bronchitis and pneumonia)
• asthma (secondhand smoke is a risk factor for the development of asthma and can trigger attacks in those who already have it)
• coughing, sore throats, sniffling, and sneezing
• cancer
• heart disease

So secondhand smoke doesn't just impact a person in the future. It can cause problems right now, like affecting someone's sports performance or ability to be physically active.

What Can You Do?

Chances are, you know someone who smokes. Maybe it's your Grandma or the guy you hang out with at your job at the mall. Whether you smoke or you're regularly around someone who does, it's never healthy to breathe in tobacco smoke. Even occasional or short-term exposure can take a toll on the body.

If you smoke, try to quit. Quitting isn't easy because smoking is highly addictive. But plenty of programs and people can help you make the brave effort to becoming smoke free. And just consider the benefits: You'll look, feel, and smell better, not to mention you'll have more money saved to go out and show off the newer, healthier you! Who knows — maybe knowing that you're protecting the people you love by quitting will help give you even more willpower to kick the habit.

If you don't smoke, ask the smokers you know to observe these two practical habits:

1. Take all their smoke breaks outside — away from other people, especially kids and anyone who's pregnant. Smoke lingers in the air hours after cigarettes are put out. That means if a smoker is puffing away anywhere inside, other people are inhaling that smoke, too. Because smoke sticks to people and their clothing, when smokers come back inside, they should wash their hands and change their clothing, especially before holding or hugging children.
2. Never smoke in a car with other people. Even exhaling out the window does little, if anything, to reduce smoke exposure.

It's been scientifically proven that secondhand smoke is dangerous. So, hopefully the smokers in your life will be willing to take these simple steps.

Just as a person who smokes chooses to light up, nonsmokers have a choice, too — to walk away from other people's smoke at home, school, work, restaurants, even friends' and family members' houses. New laws are making it easier all the time for nonsmokers to lead smoke-free lives.

Taking a stand on secondhand smoke will keep you much healthier and possibly even help someone you love think twice about their own unhealthy habit, too.

Reviewed by: Steven Dowshen, MD
Date reviewed: November 2011